Optical interferometers have been used in the field of examining the profile of an optical element such as a lens or a prism. Namely, the light from a laser source is separated into two beams, and one of these beams is passed through a test piece (hereinafter referred to as “sample”) such as a lens or a prism. After that, these two beams having been separated are put together, wherein an interference fringe is produced. This interference fringe is observed to measure the aberration of the lens or the flatness of the prism. In this method, the difference in the subtle optical properties generated in the sample can be enlarged by using the interference fringe to detect.
A spectrometric analyzer is known which employs a similar optical interferometer to detect wavelength component contained in the reflected light from the sample, thereby analyzing the elements contained in the sample. White light containing all the wavelengths in the measurement range is applied to the sample, and the light reflected therefrom is separated into two beams, similarly to the aforementioned case. The length of the optical path of one of these beams is changed on a continuous basis so that a difference in optical path is given between the separated beams. After that, two beams having been separated are put together to cause interference. Changes in the intensity of the interference light are measured to detect the wavelength components contained in the reflected light.
In the meantime, a method is proposed in which an interferometer for the spectrometric analyzer is made by using the MEMS (Micro-Electromechanical Systems) technology as a microfabrication technology based on the semiconductor process. For example, Non-Patent Document 1 discloses a phase shift type spectroscope in which one of two mirrors is fixed in position and the other mirror is moved to cause interference of the reflected light.
Patent Document 1 discloses a lamellar grating interferometer as an interferometer for spectrometric analyzer in which one of comb-toothed lamellar gratings is fixed in position and the other is moved to cause interference.
Further, although this is different from the spectrometric analyzer, Patent Document 2 discloses an optical modulation element in which the MEMS technology is used to form a fixed mirror and a movable mirror, and the movable mirror is moved by electrostatic force with respect to the fixed mirror, thereby causing optical interference between the fixed mirror and the movable mirror. This optical interference is used to perform optical modulation. The same Patent Document also discloses a flat panel display element in which the aforementioned optical modulation elements are arranged and are driven individually to form an image.